Many electronic devices use touch screens (or touch panels) to present information to a user and also receive input from the user. For example, a touch screen is capable of intuitively and naturally capturing a user's signature. Conventional touch sensing technologies sense the position of touches on a screen. While some touch sensing technologies are able to determine a magnitude of pressure (or force) applied to the touch screen, the pressure is determined based on the area of contact (or the rate of change thereof) on the surface of the touch screen. In this regard, the prior art approximates or extrapolates an estimate of the pressure applied, but does not measure the actual force applied. Furthermore, some capacitive touch screens are responsive to mere proximity to the surface of the touch screen, that is, they may respond or react when in fact no contact or impression has been made on the surface of the touch screen. As a result, prior art systems are not able to accurately measure and resolve the pressure (or force) that is applied against the touch screen to individual locations on the touch screen. Thus, conventional authentication methods for a signature impressed on a touch screen compare the two-dimensional spatial characteristics (e.g., size, shape, orientation, etc.) of the input signature to the spatial characteristics of a stored signature. However, a skilled forger can replicate the spatial characteristics of a user's signature, and thereby compromising the integrity of the authentication.